This invention relates to an aqueous lipid standard solution which comprises water, a lipid and both an ionic and a non-ionic detergent.
Clinical chemical measurements as a rule require standard solutions, the properties of which should as closely as possible resemble those of a serum. For this purpose, the particular substance must be dissolved in an aqueous system, since only in this way will the standard sample behave like a serum. In addition, such a standard solution should not change over a lengthy period of time. These requirements are particularly difficult to meet in the case of standard solutions for the determination of lipids, e.g., cholesterol or triglycerides.
In addition to organic solvents for preparing solutions of cholesterol, the literature describes the following aqueous solvent systems for this purpose; aqueous solutions of cholesterol and non-ionic detergents are described in German Auslegeschrift 1,523,133 and in Arztl. Lab. 20, 148-151 (1974); and water-alcohol mixtures of cholesterol with added detergents are described in German Auslegeschrift No. 2,324,386. Standard solutions prepared with non-ionic detergents are stable for only a few weeks, particularly with cholesterol concentrations within the pathological range. Because of their alcohol content, standard solutions with added alcohol evaporate substantially more than does a serum sample, even if relatively high-boiling alcohols are used. Lowering the alcohol content causes the lipid to precipitate. This cannot be cured by increasing the detergent concentration since this results in an undesirably high viscosity, which can interfere with metering.
A need therefore continues to exist for a lipid standard solution which is free of the aforementioned disadvantages.